1. Field of the Invention
The invention relates to an exhaust gas line of an internal combustion engine which includes at least one catalytic converter that is provided with at least one support for the converter arranged in a housing and which includes at least one first and one second area which can be flowed through in parallel, with the flow being capable of being deactivated in at least one area by means of a switching device arranged in the exhaust gas line.
The invention further relates to an internal combustion engine with an exhaust gas system and at least one water injection device for injecting water into the exhaust gas line.
The invention further relates to a cylinder head for an internal combustion engine with liquid cooling and including a liquid-cooled exhaust manifold which is arranged integrally with the cylinder head, with the cylinder head includes at least one first cooling chamber.
2. The Prior Art
An exhaust gas line with a catalytic converter with supports for the catalytic converter is known from DE 36 29 945 A1, with the supports being arranged concentrically with respect to each other and both can be flowed through parallel with respect to each other. The exhaust gas flow is divided into two exhaust gas ports downstream of the supports for the catalytic converters. By a switching device arranged in an exhaust port one of the two supports can be deactivated. A mutual influence of temperature of the supports for the catalytic converter can thus be achieved, so that the temperature range which is most beneficial for the aftertreatment of the exhaust gases can be reached more quickly or can be held in a more secure manner.
DE 102 01 042 A1 discloses an exhaust system for an internal combustion engine with a catalytic exhaust gas converter, comprising a housing, a support for the converter held in the housing and an intake manifold. A swirl generator is arranged in the intake manifold which leaves open a central flow path. The support for the converter comprises an inside area and an outside area, when seen in the axial direction, with the cell density of the flow conduits in the inside area being larger than in the outside area and/or the inside area is arranged with a higher catalyst activity than the outside area. An active changeover possibility is not provided between the two areas.
DE 199 38 038 A1 describes an exhaust gas treatment apparatus with varying cell density, with the densities of the cell groups being arranged in such a way that an even flow through the entire substrate is promoted.
DE 92 01 320 U1 further discloses a catalytic converter apparatus for internal combustion engines in which at least two exhaust gas intake manifolds and at least two gas outlet manifolds are connected to the housing enclosing the catalytic converter substrate whose cross-sectional surface areas on the inlet and outlet side are each opposite to different areas of the associated face surfaces of the substrate. A variation depending on the operation of the exhaust flow guidance through the catalyst substrate can be performed with and without several flow deflections via shut-off devices arranged on the intake and outlet side. A sufficient exhaust-gas-cleaning effect shall thus be achieved under the highest number of possible operating conditions of the internal combustion engine. Areas with different physical and/or chemical properties concerning the response behavior, the permeability, the catalytic activity and/or thermal inertia are not provided.
The dimensioning of the cross section and the permeability of the catalytic converter represents a compromise between a surface sufficiently loaded with noble metal for ensuring a rapid light-off during cold starting and low pressure loss at nominal power. The former occurs in the case of highly effective catalytic coatings at a given space and high cell densities; the latter profits in contrast from low cell densities.
This target conflict is solved in the state of the art for example by switching behind one another a first catalytic converter support with a high cell density and short length and a second catalytic converter support with a rather low cell density but with a larger length and larger diameter which can be separate in the exhaust line or can also be combined in a housing. A further embodiment which comes with a stronger compromise in comparison with the first embodiment uses a single catalytic converter support which is provided on its gas intake side on a certain length with a especially highly effective catalytic coating, but is provided on its remaining length with a comparatively normal coating, so that this is known as zone coating. Further embodiments which might surely be advantageous with respect to the function but would require a large amount of constructional work such as catalytic converter supports which are supplied in a cascading switchable manner are not used due to their complexity. Electrically heatable catalytic converter supports for rapid light-off, which for this reason could be arranged in a larger way and with lower pressure loss according to requirements at nominal power, require metal as a support material and a respective electric supply and are currently hardly used due to high costs.
Future spark-ignition engine concepts which allow us to expect a special doubling of currently common specific output through multi-stage turbo charging with respectively extreme spreads of lowest and maximum exhaust volume flows and moreover require low exhaust gas counter-pressures under full load and nominal power will be difficult to operate with the known simple constructional solutions. Complex constructional solutions such as cascade arrangements will soon meet limits through available space. Moreover, the heating-up behavior will be additionally impaired by a rising amount of wall surfaces significantly additionally in contact with exhaust gases through multi-stage turbo charging concepts.
The adherence to component temperature limits in the catalytic converter and/or turbocharger is currently ensured by using the evaporation heat of additionally injected fuel. As a result, a rich mixture is present in a considerable part of the operating characteristics, which is primarily responsible for the clearly marked difference between cycle consumption and practical consumption as compared to diesel engines. This problem increases with rising specific output and presents a target conflict for highly charged down-sizing engine concepts whose purpose was to reduce consumption in real vehicle operations.
Especially turboengines can be operated with a stoichiometric mixture even under full load and nominal output in a manner allowing an exceptionally low consumption with consumption improvements at nominal output of between 15% and 30%, and absolute values around approximately 260 g/kWh when other measures such as enrichment are used for cooling purposes. In real driving operations, the savings can be in a magnitude of 5% to 20%, depending on driving profile, combination of engine and vehicle, and fuel quality.
Two approaches are currently known in order to achieve the improvement in consumption:    1) Use of materials resistant to high temperatures for exhaust manifold, turbine and catalytic converter in order to reduce the need for enrichment by shifting currently typical turbine intake temperatures of 950° C. to 1000° C. to 1050° C. In addition to significantly higher costs and increasing problems with the catalytic converter supports for example, thermomechanical problems and heat radiation, the potential is limited in this case. Especially when operations are conducted with unfavorably hot ambient conditions and cheaper fuels with lower octane numbers, the temperature threshold again needs to be maintained by increased enrichment.    2) A higher potential than an increase in the temperature limit is the inclusion of the exhaust-conducting pipes before the turbine in a water-cooled cylinder head for example, as was described in the Austrian patent application A 1216/2005 for example. Gas cooling is not carried out directly in this case, but indirectly by heat transfer at the outside surfaces. By providing a respective configuration, a broader effective range can be ensured than with raising the temperature limit and the need for additional enrichment is potentially lower. A relatively low production effort can be achieved by high system integration. The heat is discharged through the cooling water circulation however and at speeds beneath maximum torque one must take a certain loss of torque in turboengines into account because a minimum flow through the water jacket and thus a cooling for limiting boiling of the water must be maintained, thus leading to a lower energy content of the exhaust gas.
It is known from WO 98/10185 A1 to inject water for NOx reduction before a turbocharger into an intake system of an internal combustion engine. A similar system is known from JP 56-083516 A.
U.S. Pat. No. 5,131,229 A discloses a turbo internal combustion engine with external exhaust gas recirculation, with water being injected into the exhaust gas stream for NOx reduction. The water is taken from a tank which is heatable for protection against freezing.
U.S. Pat. No. 6,151,892 A1 discloses an internal combustion engine with programmed water injection into the exhaust gas system in order to change gas dynamics for improved adjustment to cylinder scavenging. As a result, the oscillation length is influenced by changing the exhaust gas temperature.
An exhaust gas system for an internal combustion engine is further known from U.S. Pat. No. 6,357,227 B1, with a condensation water collector being provided which is provided upstream of a device for cleaning the exhaust gas and is connected with the exhaust gas line in respect of flow. The condensation water collector is connected with a water reservoir which is connected in respect of flow with a reservoir for a reducing agent for a catalytic converter. The water which is guided in the exhaust gas line can condensate before entering the exhaust gas aftertreatment device. The disadvantageous aspect is that water is taken from the untreated exhaust gases upstream of the exhaust gas aftertreatment device for the condensation device, as a result of which the condensation system is subjected to high contamination. A permanent function of this system is therefore not ensured.
It is known from US 2005/0087154 A1 to arrange the exhaust port integrally with the cylinder head. The main cooling chamber formed by an upper and a lower partial cooling chamber is thermally connected with the exhaust port. A separate control of the cooling of the exhaust port is not provided.
It is the object of the present invention to solve this target conflict with comparatively little additional effort and to enable optimal exhaust gas cleaning in nearly every operating range of the engine.
It is also the object of the invention to considerably reduce fuel consumption.
It is a further object of the invention to enable setting the cooling of the exhaust manifold, independent of the cooling chamber of the cylinder head.